LME49724: using dc servo to remove offset voltage on the outputs

Iniv Issor

Part Number: LME49724

See attached schematic of LME49724, with dc servo circuit to null dc offset voltage on the outputs.

The input to the LME49724 is the summation of two signals.

Note: I realize that I should add another 0.1uF cap across R55 (so it is the same as R54).

- Is this the correct way to implement a dc servo with the LME49724?

- Is there a better choice of part to use for the dc servo than the LT1097S8?

Thank you

over 3 years ago

0 Justin Beigel over 3 years ago

TI__Mastermind 18545 points

Hello,

Our team is looking into this thread and will respond as soon as possible.

Best Regards,
Justin Beigel

0 Iniv Issor over 3 years ago

Prodigy 30 points

Ok - thank you, Justin.

0 Ivan Salazar over 3 years ago in reply to Iniv Issor

TI__Guru** 102045 points

Hi Vinnie,

I would suggest to use the available simulation models to verify the servo amplifier on the feedback loop is not affecting the device operation. I haven't seen these servo amplifiers in differential amplifiers like LME49724.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

0 Iniv Issor over 3 years ago in reply to Ivan Salazar

Prodigy 30 points

Hi Ivan,

Can you show this to someone in the engineering team that is familiar with using a servo with a differential amp like this?
I don't believe I am breaking any new ground with this idea ;-)

The input is a single-ended (summing amp) via R46 and R47.

Ltspice simulations look good, but I was just hoping that someone very familiar with the LME49724 (and servos) can chime in.

Thank you,

Vinnie

0 Ivan Salazar over 3 years ago in reply to Iniv Issor

TI__Guru** 102045 points

Vinnie,

Will ask precision amplifiers team to take a look if possible, this is not common in audio applications.
However as long as simulations are OK I would say it is fine to implement.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

0 Iniv Issor over 3 years ago in reply to Ivan Salazar

Prodigy 30 points

Ok - thank you, Ivan!

Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

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LME49724: using dc servo to remove offset voltage on the outputs